1. Field of the Invention
This invention relates to a one-part, water based, silicone elastomeric composition useful as a fire barrier.
2. Background Information
Ramseyer, in U.S. Pat. No. 3,623,904, issued Nov. 30, 1971, disclosed a method of protecting aerospace vehicles by coating with a composition of silicone elastomer, silicon carbide, silica, and high temperature decomposing fiber such as carbon fiber. The fibers prevent the char from flaking off when the coating is subjected to the high temperatures and velocities encountered upon reentry to the earth's atmosphere.
An improved fire retardant siloxane foam is taught by Hitchcock in U.S. Pat. No. 4,259,455, issued Mar. 31, 1981, which adds aluminum silicate as a ceramic fiber to a composition of organohydrogensiloxane, hydrated organosiloxane, and platinum catalyst. The fiber is preferably a milled fiber. The fiber makes up from about 30 percent to about 40 percent by weight of the total composition.
Daroga et al. describe in U.S. Pat. No. 4,286,013, issued Aug. 25, 1981, a lightweight sheet useful as a flame barrier which comprises a sheet having a coating of diorganopolysiloxane gum, fibrous filler, hollow glass microspheres, and curing agent. The fibers, typically 700 micrometers long, improve the coherence of the coating when exposed to flame.
A cured polyorganosiloxane foam exhibiting high resistance to burn through and disintegration when exposed to flame is disclosed in U.S. Pat. No. 4,433,069, issued Feb. 21, 1984, to Harper. The cured foam contains at least 5 parts by weight of platinum per million parts by weight of foam with at least 0.1 percent by weight of at least one finely divided non-metallic, fibrous heat resistant material, and at least 0.1 percent by weight of at least one finely divided non-metallic, cellular heat resistant material dispersed in a cured, cellular polydiorganosiloxane. The combined concentrations of fibrous and cellular heat resistant materials do not exceed 40 percent by weight of the total weight of the foam. The preferred method of making the foam forms a homogeneous reactive composition by blending together at least one organohydrogensiloxane, at least one hydroxyl compound, and at least one polydiorganosiloxane with the above ingredients.
A composition of mineral particles bound with silicone elastomeric emulsion is taught by Meddaugh in U.S. Pat. No. 4,505,953, issued Mar. 19, 1985. The mixture of aqueous silicone elastomeric emulsion and mineral particles is useful as a coating. The cured coating has flame retardant properties.
Silicone foams have been produced from aqueous emulsions of silicone polymer. A method disclosed in U.S. patent application Ser. No. 665,224, filed Oct. 26, 1984 assigned to the assignee of the instant application and now U.S. Pat. No. 4,572,917, makes use of organic fibers to stabilize a froth formed of silicone emulsion and fibers which dry to give a foam.
One of the most successful methods of producing flame resistant coatings combines polydiorganosiloxane as a binder that is cured in the presence of platinum, preferably using the platinum as the curing catalyst. This method, although effective, is very expensive because of the cost of the platinum. A method of producing flame retardant coatings and sealants without the use of platinum is desired. It is also desirable to be able to apply coatings in thicknesses of greater than 10 mm to provide flame resistance for long periods of time, hours for example, without the coating material cracking during exposure to flame. An economical material that could be stored in one part and then be used to fill openings in fire walls to prevent the passage of fire and smoke through the wall that was easy to apply was needed.